Pencil



F. C. DEL! Aug. 28, 1928.

PENCIL Original Filed Oct. 3, 1921 w gg Patented Aug. 28, 1928.

UNITED STATES FRANK C. DELI, OF CHICAGO, ILLINOIS, ASSIGNOR T AU'roPoIN'r COMPANY, or

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

PENCIL.

Original application filed October 3, 1921, Serial No. 504,839. Divided and this application filed December 30, 1924.

My invention relates to mechanical pencils and particularly to a peculiar plunger construction for use in connection therewith. This application is a division of my co-pending application, Serial No. 504,839, filed October 3, 1921, now Patent No. 1,552,123, Sept. 1, 1925.

In the commercial manufacture of mechanical pencils of the type in which a threaded plunger is utilized, it is important that the co-acting threads on the tube and plunger be firm and rugged in construction in order to withstand the hard usage to which pencils are subsequently subjected. In the pencil of my invention, the lead tube with which the plunger co-operates, is provided with helical grooves corresponding to threads. The plunger for cooperation therewith consists of a wire having its head flattened, the threads for cooperation with the helical groove in the tube being formed by one stroke of a die in which the metal is flattened at diametrical ly opposite points and caused to flow outside of the normal contour of the wire. This results in the formation of lateral projections from the wire.

The invention will be more readily understood by reference to the accompanying drawings, in which,

0 Fig. 1 is a sectional view through a pencil constructed in accordance with my invention. 0dFig. 2 is a face view ofa half of a pencil y i Fig. 3 is a sectional viewthrough the completed pencil on the line 33 of Fig. 1, and

Fig. 4 is an elevation of the tip, tube and plunger.

In the drawings, it will be seen that my invention isintended for use in connection with 10 a pencil body preferably composed of-bakelite .or similar material, the body being initially formed in two halves, 10, 11, the halves being subsequently welded by heat and pressure into an integral cylindrical barrel having a recess 5 12, in its upper end for the accommodation of the reserve leads, a fiat recess, 13, at its intermediate portion, and a round axial opening 14, at its lower end. At its upper end, the body is reduced to provide a seat for a cap 15, and an eraser, 16. At its lower end the body is similarly reduced to provide a seat for the eylindrica portion 17 of the tip 18.

Firmly secured by welding or otherwise in Serial No. 758831.

the tip is the lead tube 19, the tube having a peripheral, helical groove, 20, formed therein. the internal groove between adjacent turns of the rib constituting the threads. The tube is loosely fitted within the circular recess 14.

The plunger consists of a stem or shank 21, having its upper end flattened as at 22, to slide within the flattened recess, 13, in the intermediate portion of the body. The width and thickness of the flattened portion and the recess are correlated in order that the plunger may be prevented from turning, but permitted to slide. At a point near the lower end, as best shown in Fig. 1, the plunger is acted upon by a die in such manner that the metal is caused to flow laterally, thereby forming the projections 23, 24, from the side faces of the round wire plunger. Each pair of projections constitutes to a thread. It will be noted that by the use of, a single pair of dies and so disposing the stem relative thereto that the projections are vertically offset, the projections engage with opposite portions of the same helical groove. By employing a stem of ample size, the body thereof may be reduced locally suflicient to form the lateral projections without unduly weakening the stem.

I claim 1. In a pencil, the combination of a body, and lead-advancing mechanism including a plunger, said plunger having side projections that act as threads, said projections being formed of metal that has been displaced laterally from the body of the plunger.

2. A plunger for use in mechanical pencils, said plunger consisting of a length of wlre having a plurality of lateral projections corresponding to threads, the metal in the lateral projections being composed of a portion of the metal of the body of the plunger that has been displaced laterally.-

3. A lead propelling plunger composed of a length of wire, one end of which is flattened and the opposite end of which is provided with a plurality of separate, non-continuous lateral projections composed of metal displaced from the body of the wire by locally reducing the cross sectional area thereof.

Signed at Chicago, Illinois, of December, 1924.

FRANK C. DELI.

an operating unit, corresponding this 19th day 

